Electronic devices containing active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices. Devices containing active organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.
An OLED may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.
Holes are injected into the device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LUMO) of a light-emitting material combine to form an exciton that releases its energy as light.
A light emitting layer may comprise a semiconducting host material and a light-emitting dopant wherein energy is transferred from the host material to the light-emitting dopant. For example, J. Appl. Phys. 65, 3610, 1989 discloses a host material doped with a fluorescent light-emitting dopant (that is, a light-emitting material in which light is emitted via decay of a singlet exciton).
Phosphorescent dopants are also known (that is, a light-emitting dopant in which light is emitted via decay of a triplet exciton).
Bernius et al, “Progress with Light-Emitting Polymers”, Adv. Mater. 2000, 12(23), 1737-1750 discloses conjugated polymers for use in organic light-emitting devices including polyphenylenes, polyfluorenes and polyphenylenevinylenes.
EP 1741149 discloses polymers comprising 2,7-linked phenanthrene repeat units.
US 2010/288974 discloses polymers comprising 3,6-linked phenanthrene repeat units.
US 2007/0191583 discloses polymers based on 3,6- and 2,7-linked phenanthrenes.